Jamie Oliver will be distraught. The TV chef's bid to banish fatty foods from school dinners has had an unintentional side effect - sales of Turkey Twizzlers, the junk food he loathes above all others, are soaring.

Oliver hit out at the product, which contains only 34% turkey, in his Channel 4 series Jamie's School Dinners. He joked he was going to send a bomb to the factory of Turkey Twizzlers' manufacturer, Bernard Matthews.

But Oliver's attacks appear to have backfired after the Norfolk-based company revealed sales of Turkey Twizzlers are up nearly a third compared with the same period last year.

"We were picked out by Jamie Oliver because everyone has heard of Bernard Matthews, yet we are a company that has been responding to health concerns for years and going down the low-fat route," said David Joll, the managing director of Bernard Matthews.

"A Twizzler has much less fat than a sausage, yet we don't hear Jamie Oliver telling people not to eat sausages. We have been unfairly treated over a turkey product, which is the least fatty of all meats."

Jamie's School Dinners was a critical and ratings hit for Channel 4. It finished with 5 million viewers and was credited with forcing the government to promise improvements in the quality of school food.

Oliver went to work in a school in south London, where he found children were fed on a budget of just 37p a meal.

The chef, who launched a stinging attack on Turkey Twizzlers in the show, turned on Sainsbury's for stocking the product during a debate in London to support the series. Unbeknown to Oliver, however, the supermarket stopped selling them in 2003.

Tests revealed Twizzlers had 21.2% fat when cooked, more than twice the 10% maximum recommended for processed meats in Scotland, where they have been withdrawn from schools. However, they are still being sold in dozens of schools in England. Bernard Matthews said the fat content was only 7%.

A spokesman for the company said sales were up 32% over the past four weeks, compared with the same period last year. Mr Joll said the company had "no plans to withdraw the product".

The education secretary, Ruth Kelly, has pledged to improve the quality of school catering but has stopped short of promising extra cash. She has denied climbing aboard the bandwagon Oliver's show started.